1. Field of the Invention
The present invention relates to an image pickup apparatus which records a digital image signal by photographing an object, and which transfers the recorded digital image signal to an external device. The present invention also relates to the external device connected to the image pickup apparatus, and to an image pickup method.
2. Related Background Art
Conventionally, in an image pickup system including an image pickup apparatus such as a digital camera and an external device connected to the image pickup apparatus through a communication means of the image pickup apparatus, a picture taking operation is performed with priority by interrupting transfer of a digital image signal representing a photographed image to the external device when a photography preparation instruction is given by a user during transfer of the image signal (Japanese Patent Application Laid-open No. 2000-134531).
In the conventional image pickup system, however, when a picture taking operation producing a digital image signal and transfer of the produced digital image signal are performed simultaneously with each other, there is a possibility that the amount of data of the digital image signal produced by picture taking exceeding that of the transferred digital image signal, because the picture taking operation is performed with priority over the transfer operation. In such a case, the image memory for temporarily storing the digital image signal produced by picture taking, which is provided to the image pickup system, is filled to capacity, and the image pickup apparatus becomes unable to perform a new picture taking operation. To newly start picture taking, the user must restart the transfer operation by canceling the photography preparation instruction or a picture taking instruction to provide an open area in the image memory necessary for the next picture taking.